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How to Create an Awesome Diagnostic Drive for Your Mac

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Mac not booting? Software update went wrong? Need to do a reinstall? These are just some of the reasons why having a diagnostic drive available is something that we all should have (in addition to a good backup strategy, of course). In this tutorial, we’ll be setting up an old external USB drive with some essential software to allow us to boot, fix and reinstall software on a Mac.

Having a diagnostic drive available is something that we all should have...

What is a Diagnostic Drive?

Essentially, it’s an external hard drive that you set up so that you can recover from different scenarios where your beloved Mac could go wrong. Examples of these include:

  • A software update crashed, leaving us without a bootable Mac.
  • You installed a driver and now your Mac kernel panics when you try to log in.
  • A user has forgotten their password.
  • The built-in hard drive is reporting errors and you need to recover data, fast!

Once set up, our diagnostic drive will contain the following:

  • A full installer for OS X Mountain Lion.
  • A standard installation of OS X Mountain Lion.
  • Some simple but useful utilities to resurrect a troublesome Mac.

Let’s quickly go over each of these services that our drive will do.

A Full Installer for OS X Mountain Lion

Before Lion, if you ever needed to do a reinstall of OS X, you had to have your installation DVDs handy. When Lion was released, it was Apple’s first OS that required no installation media, you just download and intall it.

Lion set up a secret recovery area on your hard drive so if you needed to reinstall Lion, you could boot up your Mac while holding down ⌘R

In addition, it brought with it the innovative feature called Recovery. Lion set up a secret recovery area on your hard drive so if you needed to reinstall Lion, you could boot up your Mac while holding down ⌘R. From here, you’d sign in with your Apple ID and it would automatically download Lion again and install it. Great!

Lion Recovery can boot your Mac and download the files needed over the internet
Lion Recovery can boot your Mac and download the files needed over the internet

But what if you don’t have immediate access to the Internet? Or you’ve had a brand-new hard drive fitted? Our diagnostic drive will have the full installer available so if you ever need to perform a reinstall of OS X, you can.

Our diagnostics drive will include all the required files for a complete installation
Our diagnostics drive will include all the required files for a complete installation

Tip: Because the App Store allows you to install any apps you purchase on any computers you own, you can use the diagnostic drive to install OS X on all your Macs without having to download Mountain Lion on every Mac!

A Standard Installation of OS X Mountain Lion

The next element of our diagnostic drive is a basic “known-good” installation of OS X. Remember when you last bought a new Mac (or performed a clean install) and the only thing it had on it was OS X? This is what we’re going to do. In some ways, this is even more useful than the installer. With a basic installation of OS X on our diagnostic drive, we can boot a Mac that otherwise won’t boot.

Having a clean install of OS X lets us eliminate possible 3rd party problems
Having a clean install of OS X lets us eliminate possible 3rd party problems

Tip: Known-good is a phrase often used with Apple technicians used to describe something we know is definitely working. In the case of our drive, we’ll be installing a basic, no-frills version of OS X that we know works.

We’ll load our standard installation with a select few utilities and essential pieces of software. As we won’t be using it on a daily basis, we’ll know it’s working should we ever need to use it.

With a basic installation of OS X on our diagnostic drive, we can boot a Mac that otherwise won’t boot.

Getting Our Diagnostic Drive Ready

Before we begin, we first need a USB hard drive. For this tutorial, I am using an old 320GB USB drive. You can use any type of USB hard drive you wish, though I recommend using a portable hard drive that doesn’t need a power supply so it’s a lot more travel-friendly and easier to use.

A portable drive makes the best kind of diagnostic drive as it doesn’t require a separate power supply
A portable drive makes the best kind of diagnostic drive as it doesn’t require a separate power supply

Tip: You can even use a 64GB USB thumb drive, but it is far from ideal. I recommend at least a 128GB drive or above.

Download Lion DiskMaker

Now we’ve got our USB drive ready, we will need to download the application Lion DiskMaker. This great utility will help us create the installer section of our diagnostic drive. It’s free (donations accepted) and works with both Lion and Mountain Lion.

Lion DiskMaker lets us create fully working installers for Lion and Mountain Lion
Lion DiskMaker lets us create fully working installers for Lion and Mountain Lion

Download OS X from the Mac App Store

The drive I will be creating will be using Mountain Lion. (If you only have Lion, the instructions are still the same). I purchased it just after it was released and upgraded my MacBook Air. The installer deletes itself after it has done it’s job, so we need to download it again. With the Mac App Store we can just download it again (for free).

Our diagnostic drive will save having to download OS X again and again
Our diagnostic drive will save having to download OS X again and again

Tip: Mountain Lion weighs in at just over 4GB, so ensure you’re not nearing any data caps and have a decent speed!

Launch the App Store and click Purchases. From here, you can download and install any app you’ve already purchased. You will see among your most recent purchases is OS X Mountain Lion. Click Download and the installer will start downloading. Once finished, it’s likely to open automatically - just quit the app when it does.

The App Store allows you to download any previous purchases, even if they’re not available anymore
The App Store allows you to download any previous purchases, even if they’re not available anymore

Preparing Our Diagnostic Drive

For the next part of our tutorial, we’re going to do the following:

  • Partition our USB drive in to three partitions.
  • Use Lion DiskMaker to clone the Mountain Lion installation software to one partition.
  • Perform a standard install of Mountain Lion to another partition.

Phew! Sounds like a lot! Don’t worry, I’m not going to make you read page upon page of text to achieve this! Instead, I am going to show you using a screencast.

What’s Partitioning?

Partitioning is pretty much what it sounds like. We’re going to “partition” our hard drive into 3 sections. Each partition is treated like a different hard drive, and we can have each partition do different things. Think of a big room in your house and you’ve decided “You know, this room is too big, but if I split it into two rooms, that would be much better”.

Tip: Apple refers to partitions as volumes. The terms are pretty much interchangeable.

To do that, you put up a partitioning wall. Think of your external drive as the room. You can add the partitioning wall anywhere in the room, but the bigger you make one side, the smaller the other side will be. When you’re finished, you have two new rooms, but it’s still within the same single master room. They can both be used completely separately. This is the same as our hard drive, one partition can be used and it won’t interfere with another. We could delete all the data from one partition and not risk any data in another.

Screencast


How to Create an Awesome Diagnostic Drive for Your Mac

The Drive in Action

Now we’ve got a working installer and installation of Mountain Lion on our diagnostic drive, it’s time to give it a whirl. First, open System Preferences and select Startup Disk. With the drive attached, you should see the following screen:

OS X’s Startup Disk will display all available bootable partitions
OS X’s Startup Disk will display all available bootable partitions

If you see the same as above, then your drive is ready to go! To use your drive, simply plug it in to your Mac and boot it up, holding down the Alt key. You’ll get a menu that will let you select which partition to boot from!

Examples of Using the Diagnostic Drive

There’s a number of different scenarios where having a diagnostic drive will come in handy (we’ve covered a few of these already).

OS X Installer

When LionMaker creates a partition, it labels it as OS X Mountain Lion Recovery Disk - 10.8 . While it doesn’t roll off the tongue, it does identify the drive!

Tip: If you’d like to rename the drive to something easier (for example, Installer) you can do so through the Finder, just like renaming a file or folder.

Apart from installing (or reinstalling / upgrading) OS X, you can also use this partition to reset a user’s password. To reset a password:

  • Boot the Mac with the installer partition
  • Click the Utilities menu item and select Terminal.
  • In Terminal, type resetpassword and press enter.
You can reset a user account’s password using the Installer partition
You can reset a user account’s password using the Installer partition

As well as being able to reset a password, you can access utilities such as Network Utilitywhich lets you test your Mac’s networking interfaces to see if there’s any problems, and Firmware Password Utility to manage the Mac’s firmware password.

Triage Partition

Before we can begin using this, we need to create our administrator account. To do this, boot your Mac using the Triage partition and you’ll eventually see the setup assistant - just like booting a new Mac for the first time. Follow the steps on the screen and create your first (and therefore the administrator) account - don’t forget a strong password!

Tip: It’s always worth booting from the Triage partition at least once a month so that you can do any software updates that might pop up.

Because we have a full version of OS X available to us, we can use tools such as Disk Utility to repair any problems or Network Utility to troubleshoot networking issues. In addition, we can include some utilities that will let us repair any problems. I’ve included a list of common utilities that are worth downloading.

  • Carbon Copy Cloner ($39.95) - An awesome backup tool that will clone your Mac.
  • Disk Inventory X (Free) - A simple disk usage utility to determine where space is being used on a hard drive.
  • DaisyDisk ($9.95) - Another disk usage utility. This one is easier to navigate but is not free.
  • Disk Drill (Free / $89) - Disk Drill provides Mac users with data recovery capabilities. If you’ve deleted a file, wiped a drive or any other type of data loss that isn’t the result of a failed hard drive, Disk Drill makes every attempt to recover it. It’s available as a free app for scanning for lost files and folders. If you need to recover any data, you’ll need to purchase a full license.
  • Drive Genius ($99) - The de-facto standard for most Apple technicians and used by Apple Store Geniuses when performing tune-ups on Macs, Drive Genius provides a suite of different tools for managing hard drives. Repair, repartition, defrag, clone and securely delete data. It’s costly, but it can repair almost any software-related drive problem.
  • DiskWarrior ($99) - The champion of Mac hard drive repair utilities. It’s been around longer than anyone can care to remember and they’ve become exceedingly good at what they do. If you had to choose between this or Drive Genius, go for this.

Learn more about Drive Genius.

Can I Only Use The Drive On My Mac?

Actually no! On of the great features of OS X is it’s ability to boot a wide range of Macs, it’s not just customised to the Mac you installed it on. As a rule of thumb, your drive will let you boot any Mac released before yours that can run Mountain Lion.

If you’ve got an iMac from 2011, this should boot it in exactly the same way as booting the Mac you created it on. Macs newer than yours may work, it really depends on what release of OS X it shipped with. As of this writing (August 2012), all available Macs that can run Mountain Lion should be bootable with this drive. If Apple were to release a new Mac mini or iMac later this year, it may need updated drivers that your drive didn’t have. Keep to the rule of thumb and you shouldn't run into any major issues.

As a rule of thumb, your drive will let you boot any Mac released before yours that can run Mountain Lion.

Wrapping Up

A diagnostic drive is something that is always worth having around. Once set up, you can keep it in a drawer should you ever need to use it. It’s something that once you’ve found a need to use it, it becomes indispensable. Not only can you use it on your Mac, but if a friend or family member suffer any problems, you’ve got something that can make you look like a hero!

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